Web search is not very profitable ever since the so-called "mobile age". A large percentage of mobile-only users have stopped relying on search, they reach to WeChat or just 100 different specific apps instead. Baidu was in desperate for growing or even keeping its ads revenue then, and they did something really bad which triggered a PR storm [1], making things worse.

Also, around 2016-2017 most of my engineer friends who are great at their job left Baidu for, surprise, ByteDance.

[1] https://en.wikipedia.org/wiki/Death_of_Wei_Zexi